There are air intake systems for engines and cabs which include an air precleaner and an air filter. The air precleaner separates particles from uncleaned air by centrifugal force (e.g., dirt, dust, chaff, sand, moisture, rain, snow, debris, and other relatively heavy particles), and the air filter has filtration media that collects particles (e.g., relatively light particles and heavier particles not removed by the precleaner) from the air partially cleaned by the precleaner, prior to ingestion by the engine or discharge into the cab.
As is well known in the art, there are various types of air precleaners, including, for example, collection bowl precleaners, aspirated precleaners, and atmosphere discharge (or ejector or ejective) precleaners. There are powered and non-powered precleaners, such as, for example, powered and non-powered ejective precleaners.
In the context of off-road machines (e.g., motor graders), it is common for such machines to have an air precleaner (e.g., ejective precleaner of the non-powered type) mounted above the hood of the engine compartment to allow intake air for the engine to be drawn from atmosphere outside the engine compartment. Often, the precleaner is mounted atop an intake tube projecting above the hood, and the precleaner is positioned such that it does not obstruct the visibility of the operator from the operator's station (e.g., laterally offset from a fore-aft midline of the machine and usually in-line with an exhaust stack in the fore-aft dimension). However, the position of the air filter within the engine compartment is constrained by other components within the engine compartment. The precleaner outlet of the precleaner and the filter inlet of the filter are thus typically offset from one another, at least laterally.
There have been machines (e.g., motor graders) that use bent tubing for the intake tube (e.g., somewhat S-shaped), above the hood in some cases and below the hood in other cases, to allow the precleaner to be positioned in a desirable location for visibility (e.g., laterally offset from a fore-aft midline of the machine and usually in-line with an exhaust stack in the fore-aft dimension) and still be able to route air from the precleaner outlet to the filter inlet. Using such bent tubing to direct air flow limits where the precleaner can be positioned due to the manufacturing constraints associated with tube bending (e.g., minimum bend radius, distance between ends).